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String.IndexOf Method (Char, Int32)

Reports the zero-based index of the first occurrence of the specified Unicode character in this string. The search starts at a specified character position.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

'Declaration
Public Function IndexOf ( _
	value As Char, _
	startIndex As Integer _
) As Integer
'Usage
Dim instance As String 
Dim value As Char 
Dim startIndex As Integer 
Dim returnValue As Integer 

returnValue = instance.IndexOf(value, _
	startIndex)

Parameters

value
Type: System.Char

A Unicode character to seek.

startIndex
Type: System.Int32

The search starting position.

Return Value

Type: System.Int32
The zero-based index position of value if that character is found, or -1 if it is not.

ExceptionCondition
ArgumentOutOfRangeException

startIndex is less than zero or greater than the length of the string.

Index numbering starts from zero. The startIndex parameter can range from 0 to the length of the string instance. If startIndex equals the length of the string instance, the method returns -1.

The search ranges from startIndex to the end of the string.

The search for value is case-sensitive.

This method performs an ordinal (culture-insensitive) search, where a character is considered equivalent to another character only if their Unicode scalar values are the same. To perform a culture-sensitive search, use the CompareInfo.IndexOf method, where a Unicode scalar value representing a precomposed character, such as the ligature 'Æ' (U+00C6), might be considered equivalent to any occurrence of the character's components in the correct sequence, such as "AE" (U+0041, U+0045), depending on the culture.

The following example demonstrates the IndexOf method.

' Sample for String.IndexOf(Char, Int32) 

Module Sample
    Sub Main()

        Dim br1 As String = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-" 
        Dim br2 As String = "0123456789012345678901234567890123456789012345678901234567890123456" 
        Dim str As String = "Now is the time for all good men to come to the aid of their party." 
        Dim start As Integer 
        Dim at As Integer

        Console.WriteLine()
        Console.WriteLine("All occurrences of 't' from position 0 to {0}.", str.Length - 1)
        Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str)
        Console.Write("The letter 't' occurs at position(s): ")

        at = 0
        start = 0
        While start < str.Length AndAlso at > -1
            at = str.IndexOf("t"c, start)
            If at = -1 Then 
                Exit While 
            End If
            Console.Write("{0} ", at)
            start = at + 1
        End While
        Console.WriteLine()
    End Sub 
End Module 

'This example produces the following results: 

'All occurrences of 't' from position 0 to 66. 
'0----+----1----+----2----+----3----+----4----+----5----+----6----+- 
'0123456789012345678901234567890123456789012345678901234567890123456 
'Now is the time for all good men to come to the aid of their party. 

'The letter 't' occurs at position(s): 7 11 33 41 44 55 64 

'

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Date

History

Reason

Clarified the relationship between string length and the startIndex parameter.

Content bug fix.

Noted that an exception is not thrown for an empty string if the index parameter is invalid.

Content bug fix.

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